title: Studies on the structure and the solution conformation of an acidic extracellular polysaccharide isolated from Bradyrhizobium.
abstract: The structure of an acidic extracellular polysaccharide isolated from Bradyrhizobium (Chamaecytisus proliferus) has been elucidated by hydrolysis, methylation analysis, and 1D and 2D 1H- and 13C-NMR spectroscopy of the complete polysaccharide. The NMR spectrum showed that microheterogeneity was present due to the minor existence of a variety of O-acetyl groups. Thus, a deacetylated sample was prepared by alkaline treatment which was then fully analysed. The deacetylated polysaccharide has the following sequence: -->3)-[alpha-D-Galp-(1-->6)-alpha-D-Glcp-(1-->3)-beta-D-Glcp-(1-->3)- alpha-D-GalpA-(1-->3)-alpha-D-Manp-(1--> The sample is partially O-methylated at position 4 of the alpha-D-Galp-(1-->6) unit. In addition, the same moiety of the native sample is also partially and heterogeneously O-acetylated. The conformational features of the deacetylated sample have been evaluated by molecular mechanics and dynamics calculations and NOE spectroscopy. The results indicate that the polysaccharide may adopt a variety of three dimensional shapes, and that there is a fair agreement between the NMR-derived distances and those provided by the calculations
authors.affiliation: Servicio Interdepartamental de Investigación, Universidad Autonoma de Madrid, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Poveda
authors.forename: M
authors.initials: M
authors.lastname: Santamaría
authors.forename: M
authors.initials: M
authors.lastname: Bernabé
authors.forename: A
authors.initials: A
authors.lastname: Prieto
authors.forename: M
authors.initials: M
authors.lastname: Bruix
authors.forename: J
authors.initials: J
authors.lastname: Corzo
authors.forename: J
authors.initials: J
authors.lastname: Jiménez-Barbero
mesh_terms: D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D008745:Methylation; D008958:Models, Molecular; D008969:Molecular Sequence Data; D008970:Molecular Weight; D019906:Nuclear Magnetic Resonance, Biomolecular; D009844:Oligosaccharides / Q000737:chemistry; D011135:Polysaccharides, Bacterial / Q000737:chemistry* / Q000302:isolation & purification; D012230:Rhizobiaceae / Q000737:chemistry*; D012996:Solutions
chemical_list: D009844:Oligosaccharides; D011135:Polysaccharides, Bacterial; D012996:Solutions